ClueLuma

Fan motor saving at differing efficiency calculator

Electrical savings compare the input needed for each shaft load at its own motor efficiency.

Units
ΔkW=0.746×(HPoldηold−HPnewηnew)\Delta \mathrm{kW} = 0.746 \times \left(\frac{\mathrm{HP}_{\text{old}}}{\eta_{\text{old}}} - \frac{\mathrm{HP}_{\text{new}}}{\eta_{\text{new}}}\right)

Calculator

Enter the values you know and leave one box empty. Calculate finds the empty one, the result or any input.

HP
HP
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kW

Worked example

Given

  • HPold\mathrm{HP}_{\text{old}} = 30 HP
  • HPnew\mathrm{HP}_{\text{new}} = 18 HP
  • ηold\eta_{\text{old}} = 0.9 —
  • ηnew\eta_{\text{new}} = 0.94 —
ΔkW=0.746×(300.9−180.94)≈10.582\Delta \mathrm{kW} = 0.746 \times \left(\frac{30}{0.9} - \frac{18}{0.94}\right) \approx 10.582

Symbols and units

SymbolMeaningUnit
ΔkW\Delta \mathrm{kW}electric input reductionkW
HPold\mathrm{HP}_{\text{old}}old actual shaft loadHP
HPnew\mathrm{HP}_{\text{new}}new actual shaft loadHP
ηold\eta_{\text{old}}old efficiency—
ηnew\eta_{\text{new}}new efficiency—

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Results are estimates for study and screening. Check the inputs, units and assumptions before you use them for design, billing or contract decisions.